4.2.1. MySQL tutorial

What is a database? ¶

Database (Database) is a warehouse that organizes, stores and manages data according to the data structure.

Each database has one or more different API for creating, accessing, managing, searching, and replicating saved data.

We can also store data in a file, but it is relatively slow to read and write data in the file.

So now we use a relational database management system (RDBMS) to store and manage large amounts of data. The so-called relational database is a database based on the relational model, which deals with the data in the database with the help of mathematical concepts and methods such as set algebra.

RDBMS is the characteristics of relational database management system (Relational Database Management System):

• 1.数据以表格的形式出现

• 2.每行为各种记录名称

• 3.每列为记录名称所对应的数据域

• 4.许多的行和列组成一张表单

• 5.若干的表单组成database

RDBMS terminology ¶

Before we move on to the MySQL database, let’s take a look at some of the terms of RDBMS:

• Database: a database is a collection of associated tables.

• Data table: a table is a matrix of data. A table in a database looks like a simple spreadsheet.

• Column: a column (data element) contains the same type of data, such as postcode data.

• Row: a row (tuple, or record) is a set of related data, such as a piece of data that a user subscribes to.

• Redundancy: twice as much data is stored, redundancy reduces performance, but improves data security.

• Primary key: the primary key is unique. There can be only one primary key in a data table. You can use the primary key to query data.

• Foreign keys: foreign keys are used to associate two tables.

• Compound key: compound key (compound key) uses multiple columns as a single index key, which is generally used for composite indexes.

• Indexes: use indexes to quickly access specific information in database tables. An index is a structure that sorts the values of one or more columns in a database table. A catalogue similar to a book.

• Referential integrity: referential integrity requires that references to entities that do not exist are not allowed in the relationship. And entity integrity is the integrity constraint that the relational model must meet in order to ensure the consistency of the data.

MySQL is a relational database (Relational Database Management System). This so-called “relational database” can be understood as the concept of “table”. A relational database consists of one or more tables, as shown in the figure:

• Header (header): the name of each column

• Col: a collection of data with the same data type

• Row: each line is used to describe the specific information of a record

• Value (value): specific information about the row, each value must be the same as the data type of the column

• Key: the value of the key is unique in the current column.

MySQL database ¶

MySQL is a relational database management system developed by MySQL AB Company of Sweden and currently belongs to Oracle Company. MySQL is an associated database management system that stores data in different tables instead of all data in a large warehouse, which increases speed and flexibility.

• MySQL is open source and currently belongs to Oracle products.

• MySQL supports large databases. It can handle large databases with tens of millions of records.

• MySQL uses the standard SQL data language form.

• MySQL can run on multiple systems and supports multiple languages. These programming languages include C, C++, Python, Java, Perl, PHP, Eiffel, Ruby and Tcl.

• MySQL has good support for PHP, and PHP is very suitable for Web program development.

• MySQL supports large databases, data warehouses with 50 million records, 32-bit system table files up to 4GB, 64-bit system supports the largest table file is 8TB.

• MySQL can be customized, using the GPL protocol, you can modify the source code to develop your own MySQL system.

Should you know before you start this tutorial? ¶

Before you start this tutorial, you should know the basics of PHP and HTML, and be able to apply them easily.

Many of the examples in this tutorial are related to the PHP language, and our examples are basically demonstrated in PHP.

If you don’t know PHP yet, you can learn about the language through our PHP tutorials.